GOP nominee David Harmer prevailed in a hard-fought, expensive four-way primary before falling short against incumbent Democrat Jerry McNerney in the general election.

The Hill also writes that the GOP’s predicament could be exacerbated by the new voter-approved open primary system under which the top two finishers in congressional and legislative races in June will compete in the November general election regardless of party affiliation.

Undoubtedly, the party is fielding plenty of calls from would-be congressional candidates who remember the GOP’s high hopes for win this district last year. And we’ve seen the GOP spent a few bucks lately on robocalls targeting McNerney, which suggests the party intends to again focus on the seat.

One 24-year-old San Joaquin County Republican, Ricky Gill, a UC-Berkeley law student, has declared his candidacy, The Hill says. And Elizabeth Emken, one of four Republicans who ran in the 2010 primary, may re-enter. My sources say Harmer, who ran unsuccessfully for Congress twice in California, is moving on to other pursuits.

But it is premature to start losing sleep over the 11th District from either political camp.

For one, this district appears likely to experience major boundary changes under redistricting. It’s a heavily gerrymandered district split by the Altamont Pass and spread across four counties. Mapping experts believe the independent map-making process now under way will produce a more compact 11th District whose party registration balance could look very different — it’s almost dead even at the moment — when it’s over. The state redistricting panel is redrawing the maps and will release drafts in early June.

A party registration gap of 5 or 6 points one way or the other in a newly constituted 11th District would make a huge difference in the predictive success — and ability to attract contributions — of any Republican challenger. And while members of Congress are not legally required to live in the districts they represent, it’s a big advantage.

Second, the top-two primary could encourage other Democrats to run against McNerney. Granted, Democrats will work hard behind the scenes to avoid such a scenario.

But the whole point of the top two primary was to provide voters a choice between the two most viable candidates by allowing them to advance to the general election even if they hail from the same party.